Colloidal Interactions between Asphaltene Surfaces in Toluene

In this paper, colloidal forces between surfaces coated with asphaltenes and immersed in toluene were measured using an atomic force microscope (AFM). Asphaltenes were coated on silica wafers and silica spheres using two methods: a Langmuir-Blodgett upstroke deposition technique (LB asphaltene film) and a dipcoating method (dip-coated asphaltene film). The results showed that the repulsive interaction forces between asphaltene surfaces in toluene had a steric nature and could be well-described by the scaling theory of macromolecules. The asphaltene-coating methods were found to affect the orientation and compactness of the deposited films, leading to a substantial difference in the magnitude and range of the repulsive forces. The water content in toluene and temperature had only a marginal effect on the interaction forces. The findings provide a microscopic understanding of the behavior of asphaltenes in the stabilization of water droplets in bitumen-solvent systems.